In recent years, with the rapid spread of IT-related devices and communication devices such as a cellular phone, emphasis is placed on the development of batteries used as the power source for such devices. In the automobile industry, the development of batteries with high power and high output for electric vehicles and hybrid vehicles, has been promoted. Among various kinds of batteries, a lithium battery attracts attention due to its high energy density and output.
A lithium battery generally has a positive electrode active material layer comprising a positive electrode active material, a negative electrode active material layer comprising a negative electrode active material, and an electrolyte layer present between the positive and negative electrode active material layers. In addition, it has a positive electrode collector which collects current from the positive electrode active material layer and a negative electrode collector which collects current from the negative electrode active material layer, as needed.
A lithium battery which uses a combustible organic electrolytic solution as the electrolyte layer provided between the positive electrode active material layer and the negative electrode active material layer requires safety measures against leakage, short circuits, overcharging, etc. Especially, batteries with high power and high capacity are required to achieve further improvement in safety. Therefore, research and development of all-solid-state batteries have been promoted, such as an all-solid-state lithium secondary battery using a solid electrolyte such as a sulfide- or oxide-based solid electrolyte.
Concerning all-solid-state batteries using a solid electrolyte, it has been proposed to form the positive and negative electrode active material layers with an electrode composite material which comprises an electrode active material and a solid electrolyte, in order to increase ion conductivity of the positive and negative electrode active material layers.
For example, Patent Literature 1 discloses an electrode for lithium batteries comprising an electrode composite material layer including a mixture of a plurality of first particles and a plurality of second particles, each of the plurality of first particles containing an electrode active material and each of the plurality of second particles containing a solid electrolyte. In Patent Literature 1, the electrode composite material layer is formed by mixing the plurality of first particles each containing an electrode active material (such as LiMn2O4 or Li4Ti5O12) and the plurality of second particles each containing a solid electrolyte (such as Li0.35La0.55 TiO3), pressure-molding the mixture and the sintering the molded product.